Better known as 9-slice panels, NinePatchRect produces clean panels of any size, based on a small texture. To do so, it splits the texture in a 3 by 3 grid. When you scale the node, it tiles the texture’s sides horizontally or vertically, the center on both axes but it doesn’t scale or tile the corners.

The height of the 9-slice’s bottom row. A margin of 16 means the 9-slice’s bottom corners and side will have a height of 16 pixels. You can set all 4 margin values individually to create panels with non-uniform borders.